The damage from California's fast-spreading wildfires is usually expressed in acres destroyed, homes razed or people killed. But for the firefighters, a mental and physical toll is mounting just as fast.

Currently in the fourth year of a devastating drought, California has seen 1,500 more blazes this year than last. And those on the front lines struggling against the walls of flame are wondering when, if ever, work will return to normal.

"I have no idea when I'm going home," said Scott Gillespie as he finished a 24-hour shift fighting the 70,000-acre "Valley Fire" near Napa in what is shaping up to be a record year. As of Wednesday evening fires raging in three northern areas had consumed some 220,000 acres.

Gillespie, a 12-year veteran of the California Department of Forestry and Fire Protection, commonly called Cal Fire, says the recent conflagrations have been different and more dangerous from others the firefighters have seen. There was once a distinct fire season between April and September, he said, but no more.

"We've gotten to the point where we are ready for these fires year round," said Gillespie, one of 2,800 firefighters struggling to control the Valley Fire, which has already destroyed 600 buildings and killed one person. "We're willing to do whatever it takes to fight these things but it's taking its toll."

He says the constant demands of the job have destroyed his marriage and affected his only child.

"My five-year-old son was crying in kindergarten today" because he didn't know when he would see his father, said Gillespie. "I might not see him for another six weeks."

Frank Rodgers, a firefighter pulled in from San Mateo, three hours from the Clear Lake area where the Valley Fire is raging, said he fought a 7,000-acre blaze in February on the eastern side of the Sierra Nevada mountains, an area where there should have been a thick snow pack.

On Monday, scientists at the University of Nevada reported that the Sierra snow pack this year was at its lowest level in 500 years.

Rodgers said the longer, more intense firefighting seasons are a big change from when he joined the force 12 years ago.

"It's very stressful. At some point, it seems like it will never end," he said.

"Spitting at the fire"

Last year, Cal Fire fought 3,638 fires which burned a total of 90,848 acres.

Already this year the agency has seen 5,225 fires, which have destroyed 220,000 acres. And it is not just the sheer number of fires that is causing fatigue and stress.

Many of the blazes, like the Valley Fire, have burned with an unpredictability and malevolence rarely seen, says Scott McLean, a Cal Fire battalion chief.

He blames this on the prolonged drought and a proliferation of dense, dry undergrowth full of natural oils. Within 12 hours, and with virtually no wind, the Valley Fire had scorched more than 40,000 acres, moving at a speed that
defied computer modeling designed to predict a fire's behavior.

"We are getting extreme fire behavior without winds," said Scott Jones, a state fire behavior analyst, "The fires are traveling at speeds in excess of the models."

The small amount of rain that fell in the area on Wednesday afternoon was helpful, McLean said, but in reality "it's like spitting at the fire." He said it will take years of rain and snow to reverse the trend of longer, more dangerous firefighting seasons.

The blaze moved at such speed as it spread, that in its first hour four firefighters were overtaken by the flames and badly burned. All four are still hospitalized with first and second degree burns.

Cal Fire has about 4,300 permanent firefighters. Its ranks swell to about 6,500 at the height of fire season, and numbers are augmented by 4,300 prison inmates jailed for non-violent offences who are assigned to Cal Fire.

Cal Fire's emergency firefighting budget has increased sharply in recent years. The 2014/2015 budget is expected to end up at over $434 million, compared to $90 million five years ago.

The extra funds, which come from California's general fund, buy additional fire trucks, planes and helicopters, and help pay an expanding overtime budget. But the money has done little to expand the ranks of firefighters, which have remained relatively static, although another 150 were hired last year.

"There is no end in sight," McLean said. "We are strict about people getting rest, but there is no real respite at the moment. We haven't had a real break all year."